After release of 3rd Generation Partnership Project (3GPP) R8/9/10, the 3GPP continues to accurately research the technique of release R11 regarding the Long Term Evolution (LTE). At present, some of R8 products are available in the market, and R9 and R10 products may need to be further planned.
After stages of R8 and R9, many new features are added to R10 on the basis of the previous two releases, e.g., pilot features such as demodulation reference signal (DMRS) and channel state information reference signal (CSI-RS), transmission and feedback features supporting 8 antennae, in particular, the enhanced inter-cell interference cancelling (eICIC) technology is taken to further consider the technique for avoiding inter-cell interference on the basis of the ICIC technique in R8/9. As regards the techniques for solving the inter-cell interference problem, the technique for avoiding the cell interference in a homogeneous network is primarily considered at the initial stage of R10, with the mainstream technology considering eICIC technology and coordinated multi-point (CoMP) technology. CoMP refers to that multiple points transmit data in coordination to one or more UEs on the same time frequency resource or on different time frequency resources, and thus CoMP may reduce the inter-cell interference, improve the cell edge throughput rate, and enlarge the cell coverage. However, in the later discussion, considering the situation of more scenarios introduced into the heterogeneous network as well as the complexity of CoMP technology and the discussion time limit on R10, it is finally determined not to introduce additional CoMP standardized contents at the stage of R10, and part of CoMP requirements will be considered when designing CSI-RS, and thus there is no further discussion on CoMP technique after the 60 bis conference.
LTE defines that physical downlink control channel (PDCCH) carries scheduling and allocation as well as other control information. Each PDCCH consists of several control channels (CCEs), the number of CCEs in each subframe is determined by the number of PDCCHs and the downlink bandwidth.
User equipment (UE) obtains PDCCH by blind detection in a search space. The search space includes common search space and user-specific search space. The common search space is a region that can be searched by all UEs and carries cell-specific information; and the user-specific search space is a space range that can be searched by a single UE, the user-specific search spaces of multiple UEs may be overlapped, but the general initial search locations of the user-specific search spaces of different UEs are different. Before the UE performs blind detection, a base station generally notifies the UE, via high layer signaling, the to-be-used operating mode and the radio network temporary identity (RNTI) type used for PDCCH and subjected to cyclic redundancy check (CRC) scrambling.
The relationship among the search space Sk(L) and aggregation level L as well as the number of candidate PDCCH M(L) is shown Table 1. The aggregation level is the number of CCEs occupied by the PDCCH. When a UE performs blind detection in a user-specific search space, the UE firstly calculates an initial location Yk of blind detection according to UE ID (user identification) and subframe number, and then detects in the user-specific search space until detecting the PDCCH allocated to this UE.
TABLE 1PDCCH candidate setSearch space Sk(L)AggregationSize [number ofNumber of candidateTypelevel LCCEs]PDCCH M(L)user-specific166(UE-specific)21264828162Common41648162
The corresponding relationship between the aggregation level and the relative location of the first control channel element of PDCCH in the user-specific search space is shown in Table 2. The relative location of the first control channel element of PDCCH in the user-specific search space refers to the offset of the location of the index nCCE of the first CCE occupied by the PDCCH relative to the initial location Yk of blind detection (the relative location is represented by nCCE, offset in the present application), nCCE, offset=nCCE-Yk. As shown in Table 2, it is a schematic diagram showing a possible location of the first CCE in a user-specific search space and the corresponding aggregation level.
TABLE 2Corresponding relationship between aggregationlevel and location of the first CCEAggregationRelative location of the first CCE in theLeveluser-specific search spaceL = 1nCCE, offset = 0/1/2/3/4/5L = 2nCCE, offset = 0/2/4/6/8/10L = 3nCCE, offset = 0/4L = 4nCCE, offset = 0/8
During the discussion in 3GPP RAN1#67 related to the LTE Technology, the proposals on downlink control signaling are all substantially on enhancement of CSI-RS signaling, enhancement of DMRS signaling, enhancement of cell-specific reference signal (CRS) collision and interference problem avoidance, enhancement of PDSCH start symbol alignment and receiving, and enhancement of zero power and non-zero power CSI-RS collision and interference avoidance. The enhancement of CRS collision and interference problem avoidance, enhancement of PDSCH start symbol alignment and receiving, and enhancement of avoiding zero power and non-zero power CSI-RS collision and interference avoidance all fall within the range of rate-matching, and are collectively referred to as an interference avoidance method. In these methods, rate-matching or interference suppression may be performed according to the notified signaling, with the main reason that: in the newly added scenarios of R11, especially in Scenarios 1-3, since different points have different cell identities, the CRS location is different at different points, such that the sequences of different points are different. At this time, if different points perform joint transmission (JT), resource merging of different points cannot be aligned. If data mapping is performed independently according to the configuration of CRS, PDSCH start symbol or zero power CSI-RS of each cell, data merge errors will occur due to different Muting resource locations; and if merging is performed according to the master service point, it will cause resource waste and also introduce the interference of CRS of other points on data. In addition, for dynamic point selection (DPS), since different subframes are transmitted to a UE by different points, transmitting data according to the master service point will also cause the resource waste and the interference of CRS on data. If considering measuring the interference using zero power CSI-RS, it requires to configure more zero power CSI-RSs, moreover, if a UE configured in a zero power CSI-RS subframe of a point does not aware of the existence of the zero power CSI-RS, it may cause large influence on this UE.
As to the problem of low accuracy of downlink data rate-matching in the related art, no effective solution has been proposed at present.